Spatiotemporal variability and origin of CO2 and CH4 tree stem fluxes in an upland forest

The exchange of multiple greenhouse gases (i.e., CO₂and CH₄) between tree stems and the atmosphere represents a knowledge gap in the global carbon cycle. Stem CO₂ and CH₄ fluxes vary across time and space and is unclear which are their individual or shared drivers. This dataset contains information of CO₂ and CH₄ fluxes at different stem heights combining manual (biweekly; n=678) and automated (hourly; n&gt;38,000) measurements in a temperate upland forest.<br>This study was performed in an upland forested area at the St. Jones Reserve [39°5’20”N, 75°26’21”W], a component of the Delaware National Estuarine Research Reserve (DNERR).<br>The dominant vegetation species are bitternut hickory (<i>Carya cordiformis</i>), eastern red cedar (<i>Juniperus virginiana</i> L.), American holly (<i>Ilex opaca</i> (Ashe)), sweet gum (<i>Liquidambar styraciflua</i> L.) and black gum (<i>Nyssa sylvatica</i> (Marshall)), with an overall tree density of 678 stems ha^-1 and mean diameter at breast height (DBH) of 25.7±13.9 cm (mean±sd). We studied bitternut hickory, which is one of the most important species in the study site, accounting for 24.9% of the total basal area.<br>For code